Some scientists are backing Gareth Morgan's campaign to control cats in order to protect native species, but say more also needs to be done to counter other predators.
Morgan, a philanthropist and economist, launched the Cats to Go website yesterday, which calls for the eradication of the "friendly neighbourhood serial killer".
Killing cats was an option, but cat owners should also control their pets in order to protect native species, the website said.
University of Otago senior lecturer in zoology, Dr Yolanda van Heezik, supported Morgan's campaign, saying his proposals were reasonable and would prove effective.
"Consider using a collar with a bell: our research has shown they reduced catch by 50 per cent," van Heezik said.
"Consider keeping your cat inside at all times. This ruling is in effect already in some parts of Australia. And consider not replacing your cat when it eventually dies."
The Cats to Go website is calling for all cats to be kept inside for 24 hours a day, registered, micro chipped and neutered "while setting live capture cage traps on your property and turning the miscreants over to the local authority should be encouraged".
There were about 225 cats per square kilometre in urban areas and it was domestic cats which were the most threat to native species, van Heezik said.
"They are more likely to hunt wildlife populations to extinction, as they do not rely on wild prey for food, so they are less likely to switch to alternative sources of prey when their prey population becomes so depleted it costs too much energy to hunt for it."
Van Heezik has studied the issue and found cats brought an average of 13 prey, including rats, mice, lizards and invertebrates, back to their homes each year.
A study from the United States using kittycams, however, has shown that cats only brought back one third of what they caught and killed.
But cats weren't the only problem and the advantages of them predating on other predators needed to be considered, Landcare Research scientist John Innes said.
"In New Zealand also, cats alone cannot be blamed for the loss of any species," Innes said.
"However, they are undoubtedly key contributors to declines of some birds [and other fauna] in some places...so potentially are hedgehogs, ferrets, stoats, four wheel drive vehicles, people walking dogs and fishermen.
"In New Zealand native forests, ship rats are the major prey, and this little-seen predator eats many more birds than cats do."
When cats, ferrets and hedgehogs were the target of an eradication campaign in Mackenzie Basin, possums and Norway rats then ate the black-fronted terns, Innes said.
Cats hunt other predators, but little research has been done to show whether the negative effects of cats on native species outweighs the positive effects of their predation on rats and mice, Innes said.
"However, keeping cats inside, especially at night, will negate these possible positive effects."
- © Fairfax NZ News